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-rw-r--r--mm/mmap.c143
1 files changed, 132 insertions, 11 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index ebf19031c5e4..bdcea6310fff 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -31,6 +31,7 @@
#include <linux/audit.h>
#include <linux/khugepaged.h>
#include <linux/uprobes.h>
+#include <linux/rbtree_augmented.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
@@ -297,6 +298,27 @@ out:
return retval;
}
+static long vma_compute_subtree_gap(struct vm_area_struct *vma)
+{
+ unsigned long max, subtree_gap;
+ max = vma->vm_start;
+ if (vma->vm_prev)
+ max -= vma->vm_prev->vm_end;
+ if (vma->vm_rb.rb_left) {
+ subtree_gap = rb_entry(vma->vm_rb.rb_left,
+ struct vm_area_struct, vm_rb)->rb_subtree_gap;
+ if (subtree_gap > max)
+ max = subtree_gap;
+ }
+ if (vma->vm_rb.rb_right) {
+ subtree_gap = rb_entry(vma->vm_rb.rb_right,
+ struct vm_area_struct, vm_rb)->rb_subtree_gap;
+ if (subtree_gap > max)
+ max = subtree_gap;
+ }
+ return max;
+}
+
#ifdef CONFIG_DEBUG_VM_RB
static int browse_rb(struct rb_root *root)
{
@@ -327,6 +349,18 @@ static int browse_rb(struct rb_root *root)
return i;
}
+static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
+{
+ struct rb_node *nd;
+
+ for (nd = rb_first(root); nd; nd = rb_next(nd)) {
+ struct vm_area_struct *vma;
+ vma = rb_entry(nd, struct vm_area_struct, vm_rb);
+ BUG_ON(vma != ignore &&
+ vma->rb_subtree_gap != vma_compute_subtree_gap(vma));
+ }
+}
+
void validate_mm(struct mm_struct *mm)
{
int bug = 0;
@@ -349,9 +383,52 @@ void validate_mm(struct mm_struct *mm)
BUG_ON(bug);
}
#else
+#define validate_mm_rb(root, ignore) do { } while (0)
#define validate_mm(mm) do { } while (0)
#endif
+RB_DECLARE_CALLBACKS(static, vma_gap_callbacks, struct vm_area_struct, vm_rb,
+ unsigned long, rb_subtree_gap, vma_compute_subtree_gap)
+
+/*
+ * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
+ * vma->vm_prev->vm_end values changed, without modifying the vma's position
+ * in the rbtree.
+ */
+static void vma_gap_update(struct vm_area_struct *vma)
+{
+ /*
+ * As it turns out, RB_DECLARE_CALLBACKS() already created a callback
+ * function that does exacltly what we want.
+ */
+ vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
+}
+
+static inline void vma_rb_insert(struct vm_area_struct *vma,
+ struct rb_root *root)
+{
+ /* All rb_subtree_gap values must be consistent prior to insertion */
+ validate_mm_rb(root, NULL);
+
+ rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
+}
+
+static void vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
+{
+ /*
+ * All rb_subtree_gap values must be consistent prior to erase,
+ * with the possible exception of the vma being erased.
+ */
+ validate_mm_rb(root, vma);
+
+ /*
+ * Note rb_erase_augmented is a fairly large inline function,
+ * so make sure we instantiate it only once with our desired
+ * augmented rbtree callbacks.
+ */
+ rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
+}
+
/*
* vma has some anon_vma assigned, and is already inserted on that
* anon_vma's interval trees.
@@ -421,8 +498,25 @@ static int find_vma_links(struct mm_struct *mm, unsigned long addr,
void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
struct rb_node **rb_link, struct rb_node *rb_parent)
{
+ /* Update tracking information for the gap following the new vma. */
+ if (vma->vm_next)
+ vma_gap_update(vma->vm_next);
+ else
+ mm->highest_vm_end = vma->vm_end;
+
+ /*
+ * vma->vm_prev wasn't known when we followed the rbtree to find the
+ * correct insertion point for that vma. As a result, we could not
+ * update the vma vm_rb parents rb_subtree_gap values on the way down.
+ * So, we first insert the vma with a zero rb_subtree_gap value
+ * (to be consistent with what we did on the way down), and then
+ * immediately update the gap to the correct value. Finally we
+ * rebalance the rbtree after all augmented values have been set.
+ */
rb_link_node(&vma->vm_rb, rb_parent, rb_link);
- rb_insert_color(&vma->vm_rb, &mm->mm_rb);
+ vma->rb_subtree_gap = 0;
+ vma_gap_update(vma);
+ vma_rb_insert(vma, &mm->mm_rb);
}
static void __vma_link_file(struct vm_area_struct *vma)
@@ -498,12 +592,12 @@ static inline void
__vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev)
{
- struct vm_area_struct *next = vma->vm_next;
+ struct vm_area_struct *next;
- prev->vm_next = next;
+ vma_rb_erase(vma, &mm->mm_rb);
+ prev->vm_next = next = vma->vm_next;
if (next)
next->vm_prev = prev;
- rb_erase(&vma->vm_rb, &mm->mm_rb);
if (mm->mmap_cache == vma)
mm->mmap_cache = prev;
}
@@ -525,6 +619,7 @@ int vma_adjust(struct vm_area_struct *vma, unsigned long start,
struct rb_root *root = NULL;
struct anon_vma *anon_vma = NULL;
struct file *file = vma->vm_file;
+ bool start_changed = false, end_changed = false;
long adjust_next = 0;
int remove_next = 0;
@@ -615,8 +710,14 @@ again: remove_next = 1 + (end > next->vm_end);
vma_interval_tree_remove(next, root);
}
- vma->vm_start = start;
- vma->vm_end = end;
+ if (start != vma->vm_start) {
+ vma->vm_start = start;
+ start_changed = true;
+ }
+ if (end != vma->vm_end) {
+ vma->vm_end = end;
+ end_changed = true;
+ }
vma->vm_pgoff = pgoff;
if (adjust_next) {
next->vm_start += adjust_next << PAGE_SHIFT;
@@ -645,6 +746,15 @@ again: remove_next = 1 + (end > next->vm_end);
* (it may either follow vma or precede it).
*/
__insert_vm_struct(mm, insert);
+ } else {
+ if (start_changed)
+ vma_gap_update(vma);
+ if (end_changed) {
+ if (!next)
+ mm->highest_vm_end = end;
+ else if (!adjust_next)
+ vma_gap_update(next);
+ }
}
if (anon_vma) {
@@ -678,10 +788,13 @@ again: remove_next = 1 + (end > next->vm_end);
* we must remove another next too. It would clutter
* up the code too much to do both in one go.
*/
- if (remove_next == 2) {
- next = vma->vm_next;
+ next = vma->vm_next;
+ if (remove_next == 2)
goto again;
- }
+ else if (next)
+ vma_gap_update(next);
+ else
+ mm->highest_vm_end = end;
}
if (insert && file)
uprobe_mmap(insert);
@@ -1784,6 +1897,10 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
anon_vma_interval_tree_pre_update_vma(vma);
vma->vm_end = address;
anon_vma_interval_tree_post_update_vma(vma);
+ if (vma->vm_next)
+ vma_gap_update(vma->vm_next);
+ else
+ vma->vm_mm->highest_vm_end = address;
perf_event_mmap(vma);
}
}
@@ -1838,6 +1955,7 @@ int expand_downwards(struct vm_area_struct *vma,
vma->vm_start = address;
vma->vm_pgoff -= grow;
anon_vma_interval_tree_post_update_vma(vma);
+ vma_gap_update(vma);
perf_event_mmap(vma);
}
}
@@ -1960,14 +2078,17 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
insertion_point = (prev ? &prev->vm_next : &mm->mmap);
vma->vm_prev = NULL;
do {
- rb_erase(&vma->vm_rb, &mm->mm_rb);
+ vma_rb_erase(vma, &mm->mm_rb);
mm->map_count--;
tail_vma = vma;
vma = vma->vm_next;
} while (vma && vma->vm_start < end);
*insertion_point = vma;
- if (vma)
+ if (vma) {
vma->vm_prev = prev;
+ vma_gap_update(vma);
+ } else
+ mm->highest_vm_end = prev ? prev->vm_end : 0;
tail_vma->vm_next = NULL;
if (mm->unmap_area == arch_unmap_area)
addr = prev ? prev->vm_end : mm->mmap_base;